1. Field of the Invention
This invention is related to head restraint systems for vehicles, and more particularly to an apparatus for supporting the head of a crew member of a vehicle while the crew member is sitting in a forward lean posture during high "G" accelerations.
2. Description of the Related Art
Modern high performance fighter aircraft are capable of flight maneuvers which subject the crew members to very high accelerations, "G's." Severe stresses are placed upon the crew members by such aircraft maneuvers. Indeed, many modern aircraft are capable of aerial maneuvers which are beyond the tolerance of the human crew members. Consequently, fighter aircraft and their crew members are occasionally lost.
Several approaches have been proposed for protecting the crew member from the effects of high "G" accelerations. For example, U.S. Pat. No. 4,664,341, issued to R. J. Cummings, entitled "HEAD RESTRAINT SYSTEM" (assigned to Rockwell International Corporation), discloses a system which helps enable free and unencumbered head movement during tolerable lateral inertia forces, while locking in place and protecting the pilot's head during periods of high lateral inertia forces. The invention utilizes a helmet that rotates on a track and in an inertia reel, which will lock when lateral forces exceed predetermined levels.
Great Britain Patent No. 656,079, entitled "IMPROVEMENTS IN OR RELATING TO HEAD AND LIKE SUPPORTS FOR PERSONS SUBJECTED TO ACCELERATION FORCES" discloses a head supporting device for resisting acceleration forces on the human body. A support member is mounted to be movable in the direction of the acceleration force and is coupled to a counter-balancing mass which is subjected to the same acceleration force.
Great Britain Patent No. 978,422, entitled "IMPROVEMENTS IN SEATS" discloses the use of a helmet restraining device which is securely attached to the seat and clasps the helmet between a pair of cranked hinged arms, the arms being under the direct influence of spring influenced operating plungers, and the indirect influence of the tension springs operating on hinged detents. Several other elements are required, including slotted grid-engaging racks and wires interlinked with the slots for restraining movement of the helmet relative to the arms.
U.S. Pat. No. 3,170,659, issued to P. W. Wood, Jr., entitled "HEAD RESTRAINT FOR USE IN SPACE VEHICLES," discloses a head restraint for restraining the head movement of a crew member occupying a seat structure in a space vehicle during acceleration and attitude changes of the vehicle. The head restraint utilizes a pair of air flap members which are movably joined to opposite sides of a rear head support. The rear head support is joined to a frame member adapted for joining to the seat structure in the space vehicle. A pair of anchor blocks are joined to the frame member to laterally straddle the air flap members. A pair of adjusting means are joined to the anchor blocks for engaging the adjacent air flap member and adjusting the lateral position of each of the air flap members to restrain the head of the occupying crew member.
U.S. Pat. No. 3,376,064 discloses the use of a rigid U-shaped head encircling member pivotally attached to a head limiting member. The head encircling member is spaced from the head to allow normal movement thereof but restraining the same from unusual lateral and forward movement.
Other restraining devices are disclosed in U.S. Pat. No. 2,638,293; U.S. Pat. No. 4,004,763; U.S. Pat. No. 3,179,360; U.S. Pat. No. 3,278,230; U.S. Pat. No. 3,099,261; U.S. Pat. No. 4,339,151; U.S. Pat. No. 3,873,996; and U.S. Pat. No. 3,925,822.
Sitting in a forward lean position has been demonstrated to increase a pilot's ability to withstand the G force caused by aircraft high turns. However, in this position, it is difficult to impossible, depending on the G force, to hold one's head up. If unsupported, the head rolls forward so that the chin rests on the chest. The line of sight is thus downwards towards the floor.
None of the above-cited references addresses the specific problem as to how to effectively hold the head up while utilizing a forward leaning posture. Even if some of the above disclosed devices may be used during such a forward leaning posture, the devices are typically complex and do not allow unrestricted head movement while the crew member is in an upright position.
U.S. patent Ser. No. 07/249,794, entitled "HEAD SUPPORT/SPINE OFFLOADING EJECTION SEAT INSERT" assigned to the present assignee, discloses a seat insert insertable within the existing seat of a vehicle for maintaining a crew member of the vehicle in a forward posture during high G acceleration. The seat insert includes an elongated head support member for supporting the crew member's head during a forward leaning posture. A helmet support strap extends from the upper end of the head support member to the top of the crew member's helmet for distributing weight off of the cervical spine and for maintaining the head in an "eyes up" attitude in forward lean. A second strap extends from the upper end of the head support member to the back of the helmet for limiting head/helmet differential rotation.